Figure 7.

Schematic of XPS depth profile characterization. XPS and UPS are both based on the photoelectric effect, where an incident X-ray or UV photon of energy hν is absorbed by an atom resulting in the emission of a photoelectron. This photoelectron is of binding energy E_b and is ejected with a kinetic energy E_k, such that E_k = hν − E_b − φ, where h is Planck’s constant and φ is the work function. In (a) the spectra of a 10 nm thin layer of Ag on a TiO₂ film is measured during etching using an Ar ion gun (at 2 kV and 1 mA) 6 times at intervals of 10 s, the result being a map of the depth profile (b) of the Ag film on the TiO₂ layer where the atomic compositions are displayed in percentile measures along with their energy level occupancies [154]. Reprinted with permission from Ref [154] Copyright American Chemical Society (2014).